Install: disable step 4 (additional config info)

This fixes a security issue allowing an attacker to access the
installation script and obtain database access credentials.

Since the offending install step does not seem to be doing anything
useful, the corresponding code block has been commented out.

This vulnerability (CVE-2014-9571) was reported by High-Tech Bridge
Security Research Lab (https://www.htbridge.com/) in issue #17937
(advisory ID HTB23243).

Fixes #17939

admin/install.php

@@ -751,7 +751,12 @@ function print_test( $p_test_description, $p_result, $p_hard_fail = true, $p_mes
 # database installed, get any additional information
 if( 4 == $t_install_state ) {
 
-	/** @todo to be written */
+/*
+	# 20141227 dregad Disabling this step for now, because it does not seem to
+	# be doing anything useful and can be used to retrieve system information
+	# when the admin directory has not been deleted (see #17939).
+
+	# @todo to be written
 	// must post data gathered to preserve it
 	?>
 		<input name="hostname" type="hidden" value="<?php echo string_attribute( $f_hostname ) ?>"></input>
@@ -766,6 +771,7 @@ function print_test( $p_test_description, $p_result, $p_hard_fail = true, $p_mes
 <?php
 	# must post <input name="install" type="hidden" value="5"></input>
 	# rather than the following line
+*/
 	$t_install_state++;
 }  # end install_state == 4